Process for desulphurizing hydrocarbons



Patented Mar. 30, 1937 UNITED STATES PATENT OFF-ICE raocnss ron nasmnuaizmc nrnaocanaous Delaware No Drawing. Original application 1m 10, 1932,

Serial No. 616,574.

Divided and this application May 21, 1935, Serial No. 22,658

8 Claims. (01. 196-28) This application is a? division of our co-pending application, Serial No. 616,574, filed June 10, 1932, entitled Processes for desulphurizing hydrocarbons, wherein it is shown that certain minerals constitute effective contact agents for the vapor phase desulphurization of hydrocarbons by which a part of the organically combined sulphur is eliminated as hydrogen sulphide.

' This invention relates to processes for treating 10 sulphur bearing hydrocarbon mixtures such as natural or refinery gases, the naphtha derived from the distillation or cracking of petroleum, oil

shale distillates, and other hydrocarbon products from which the removal of certain sulphur compounds is desired.

More specifically it relates to the partial desulphurization of straight run and cracked gasolines, to which the process is particularly applicable, and the following disclosure will be limited to this application of the process for the sake of simplicity, but it will be understood that a similar procedure is followed in treating the other hydrocarbons mentioned.

To meet the specifications for motor fuel with sulphur petroleum require a drastic treatment for sulphur removal. It is well known that the method in most common use at present is objectionable from the stand point of losses in volume and quality of product, as well as of excessive cost.

To. overcome these objections, processes have been devised for sulphur removal which are based on the known catalytic action of certain contact agents on sulphur compounds in the vapor phase at elevated temperatures, in which the sulphur is eliminated as hydrogen sulphide. The present invention is an improvement of processes of this type, particularly with respect to the nature and preparation of the contact agents employed.

The catalysts proposed by-previous investigators are metals, or oxidespr sulphides of metals. Metals known to be hydrogenation catalysts have a limited usefulness in a process primarily employed to eliminate sulphur rather than to obtain hydrogenation efiects, because of their ability to cause rapid decomposition of hydrocarbons under the operating conditions with accompanying deposition of carbonaceous residues and consequent poisoning of the catalyst. Therefore, metallic sulphides, oxides, or oxides convertible to sulphides during the desulphurization process areadvantageously employed, as their action is more exclusively confined to the sulphur impurities in the hydrocarbons.

The oxides and sulphides mentioned, which are respect to sulphur content, distillates from high used in desulphurization processes, are at present? synthetically prepared as more or less pure comp unds, and are often deposited upon or admixed with more or less inactive carriers. The use and preparation of these synthetic substances is un- 5 duly expensive, and such catalysts usually have no salvage value when their usefulness as contact ents has been outlived. Undoubtedly it is for these'reasons that the general adoption of cata lytic desulphurization processes, the principles of 10 which have been long and widely known, has been so unduly delayed. Another disadvantage of the synthetically prepared agents is that their usual form is a. finely precipitated powder, which is inconvenient to handle, difllcult to maintain in a reaction chamber thru which gases are moving at a high velocity, and which tends to pack and produce a high back pressure if it cannot be incor porated in a suitable carrier.

The primary object of this invention is to pro- 20 vide a novel catalyst for use in processes for de-' sulphurizing hydrocarbons containing organic sulphur compounds as impurities, the sulphur being eliminated in the form of hydrogen sulphide,

which catalyst overcomes the several objections, 5

previously enumerated, to the speciallyprepared catalysts used by previous investigators.

' We have found that certain naturally occurring substances, containing compounds of the class mentioned above as contact agents, may be used substantially in their original state as catalysts. These substances are relatively inexpensive compared to the corresponding synthetic compound. vMoreover, their natural form is in many ways superior to the synthetic form, as the natutel crystals or lumps of these substances may be easily reduced bycrushing to a convenient and eflicient size for contact purposes-as contrasted with the powdery form of the synthetic compound. Furthermore, the natural substance is often as emcient, or even more so (in proportion to the percentage of active element present) as the prepared agent.

The naturally occurring substances referred to are metallic minerals or ores of theseminara-ls which consist of oxides and sulphides of the metals whose oxides are grouped as dehydration and dehydrogenation catalysts, e. g., aluminum, tungsten, vanadium, chromium, cadmium. zinc, molybdenum, etc. Examples of these minerals are chromite, vanadinite, molybdenite, molybdite, descloizite, ,wolframite, bauxite,'etc.

Temperatures of the order of 500--800 F. are usually necess ry. depending on (1) the particular mineral used as catalyst, (2) the time of contact between the petroleum product and the catalytic material, and (3) the specific properties of the-hydrocarbon vapor which is being desulphurv ized. Temperatures of 600-700 F. are usually preferred when straight run naphthas or cracked distillates are the products undergoing treatment. High pressures are not needed, extremely good results being obtained at atmospheric pressure. In practice it is usually desired to use pressures somewhat above atmospheric so that the vapors can be directlyconducted to a fractionator or to treating tanks for final processing.

This conversion of the organic sulphur compounds to hydrogen sulphide may be accompanied by dehydrogenation of some of the hydrocarbons present, depending on the particular catalyst and the temperature used.

The presence of hydrogen gas in the sulphur bearing petroleum vapor. aids in the conversion 'of the sulphur compounds to hydrogen sulphide from mercaptans', alkyl sulphides, etc., as hydrogen sulphide. The condensed vapors are then freed of hydrogen sulphide by a caustic wash or other suitable means.

In the practice of the present invention, the catalytic material may comprise one or more of the minerals set forth, crushed to a suitable size, usually 30-60 mesh, and possibly concentrated or diluted according to its activity. Diluents may comprise naturally associated active and/or inactive substances or substances which are suitable for diluting purposes altho not naturally associated with the catalytic material.

Example I.-Vapors of a sour cracked gasoline containing 0.142% sulphur were passed over a.

catalyst comprising a crushed ore (30-80 mesh) containing the minerals vanadinite and descloizite at atemperature of 700 1". and at a rate such that the contact time was about two seconds: The resulting product was sweet, indicating that,

the mercaptans present had been completely converted, and had a sulphur content of 0.089%.

The same catalyst also eifected a reduction of sulphur content of from 0.091% to 0.084% and i completely sweetened a sour straight run naphtha at the same temperature and flow rate.

Example IL-Chromite crushed to 30-60 mesh and maintained at a temperature of 70051". was used as the catalyst. Vapors of a sour straight run naphtha were passed over ata rate to produce a contact time of about two seconds with an.

effect identical to that described in the previous example. Prolonged w: e of this product over the catalyst failed to produce an appreciable change in its activity. In the next run over the same catalyst, 10% by volume of butyl mercaptan was added to the naphtha. The enormous sulphur content of this product was completely converted to hydrogen sulphide, as shown by testing the condensate with cadmium sulphate solution. After thissevere abuse of the catalyst, it was no longer able at the same flow rate, to produce a completely sweet product, but was sti l capable of effecting a very satisfactory sulphur reduction,

about 45%, in naphthas of usual sulphur con-' tent, and the products were only very slightly sour. The catalyst was kept in continuous operation for a period of seven days after the butyl mercaptans solution was passed over it, during which time a total of about 700 volumes (liquid) of gasoline was treated. The sulphur reduction on the final sample was substantially the same as that on the first sample, i. e., about 45% of the sulphur originally present.

Example [IL-A cracked petroleum distillate free of hydrogen sulphide was passed in the vapor phase over a catalyst comprising 30-60 mesh the sulphur content of the treated product was i 0.060 per cent as compared with 0.105 per cent on the untreated sample. Similar results were obtained with a catalyst comprising molybdite ore, except that this catalyst in the initial stages reacted with the hydrogen sulphide, thereby giving a product completely sweet to the doctor test. The molybdenum oxide was, of course, converted to the sulphide.

While it is possible to operate this process in such a way that a completely sweetened gasoline is obtained as in Example I described above, it is notmeanttobeconstruedthatsuchaproductis always obtained in actual operation. The rate of conversion of the organic sulphur compounds to hydrogen sulphide increases with both an increasedn temperature and a longer contact time between the vapors and the catalytic material. Since these factors must always be taken into consideration, it is sometimes desirable to use such an extremely short time of contact and/or such a low temperature that the resulting product. is not entirely free of mercaptans altho a substantial sulphur reduction is obtained.

Having described the invention, what 5 claimed is: I

1. The processof desulphurizing petroleum hydrocarbon fluid containing organic sulphur compounds as impurities, comprising heating the. fluid in the vapor state to a temperature within the range of 500to 800 It, contacting the vapors at substantially the same temperature with a catalyst consisting of crude mineral ore containing 'a substantial proportion of a molybdenum compound, whereby the organic sulphur compounds are decomposed into hydrogen sulphide, and separating the hydrogen sulphide from the hydrocarbon fluid. I

2. The process of desulphurising petroleum oil with a boiling point lower than the end point of kerosene, comprising vaporizing the oil. superheating the vapors containing organic sulphur compounds to a temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature for a period of about lystconsisting of crude-mineral ore containing ,a substantial proportion of a molybdenum com- ,for a period of about 2 th 10 seconds with a W.

2,070,178 pound, and separating the decomposed sulphur 10 of a molybdenum compound, whereby the mercaptans are decomposed into hydrogen sulphide, separating the hydrogen sulphide from the gasoline, and thereby obtaining a sweetened gasoline.

5. The process of desulphurizing petroleum oil 15 containing organic sulphur compounds as impurities, said oil having a boiling point lower than the end point of kerosene, comprising vaporizing the oil, super-heating the vapors to' a temperature within the range of 500 to 800 F., 20 contacting the vapors at substantially the same temperature for a period of about 2 to 10- seconds with a catalyst consisting of molybdeniteore, and separating the decomposed sulphur impurities from the oil. r

6; The process of desulphurizing petroleum oil containing organic sulphur compounds as impurities, said 011 having' a boiling point lower than the end point of 'kerosene, comprising vaporizing the oil;-superheating the vapors to a' temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature for a period oi. about 2 to 10 seconds witha catalyst consisting of'molybdite ore, and separating the decomposed sulphur impurities from the oil.

7. In a processor desulphurizing gasoline in the vapor state, the steps which comprise superheating the vapors to a temperature-within the range of about 600 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a catalyst consisting of molybdenite ore, and separating the decomposed sulphur impurities from the gasoline.

8. The process of desulphurizing petroleum hydrocarbon gases containing organic sulphur compounds as impurlties, comprising heating the gases to a temperature within the range oi-500 I to 800 F., contacting the gases at substantially the same temperature with a catalyst consisting of crude mineral ore containing a substantial proportion of a molybdenum compound, whereby the organic sulphur compounds are decomposed into hydrogen sulphide, and separatingthe hydrogen sulphide from the hydrocarbon gases.

ALBERT E. BUELL. WALTER A. scmmzu. 

